Initial scroll-blocks-on compositor integration

Source/core/rendering/RenderBox.h

Index: Source/core/rendering/RenderBox.h
diff --git a/Source/core/rendering/RenderBox.h b/Source/core/rendering/RenderBox.h
index 365afde44f203d28c04afc1d37e95cf5afb3097b..c9c41e9142c24e1214ba00ccd0e52e36a28116e3 100644
--- a/Source/core/rendering/RenderBox.h
+++ b/Source/core/rendering/RenderBox.h
@@ -76,17 +76,7 @@ class RenderBox : public RenderBoxModelObject {
 public:
     explicit RenderBox(ContainerNode*);
 
-    // hasAutoZIndex only returns true if the element is positioned or a flex-item since
-    // position:static elements that are not flex-items get their z-index coerced to auto.
-    virtual LayerType layerTypeRequired() const override
-    {
-        if (isPositioned() || createsGroup() || hasClipPath() || hasTransformRelatedProperty() || hasHiddenBackface() || hasReflection() || style()->specifiesColumns() || !style()->hasAutoZIndex() || style()->shouldCompositeForCurrentAnimations())
-            return NormalLayer;
-        if (hasOverflowClip())
-            return OverflowClipLayer;
-
-        return NoLayer;
-    }
+    virtual LayerType layerTypeRequired() const override;
 
     virtual bool backgroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect) const override;